Beech Leaf Disease is spreading rapidly throughout Connecticut, putting all of our beech trees at risk. This fatal disease is relatively new to the state and there’s a lot scientists still don’t know about its cause and how it spreads. However, there are things Connecticut residents can do to help control it, starting with the beech trees on their own property.

In this article, we cover the known facts about Beech Leaf Disease, including:

  • Which trees are affected by Beech Leaf Disease,
  • The suspected cause of the disease,
  • Symptoms to look for to tell if your trees are infected,
  • How it kills beech trees,
  • Why and how it’s spreading throughout the state, and
  • What you can do to prevent Beech Leaf Disease from killing your trees.


The information below is based on the latest research and findings from researchers around the world, including those at the Connecticut Agricultural Extension Service.

Wilting beech leaves infected with beech leaf disease

What is Beech Leaf Disease?

Beech Leaf Disease is an incurable and fatal disease of beech trees (Fagus species). It’s most noticeable in the leaves, where it causes dark bands (among other symptoms).

What causes Beech Leaf Disease?

It is almost certainly caused and spread by a foliar nematode, Litylenchus crenatae subsp. mccannii.

A nematode is a microscopic, parasitic worm. While many species of nematodes are associated with soil and plant roots, you will find this nematode on, and in, beech tree leaves.

How does Beech Leaf Disease spread?

Tree scientists and tree pathologists are still investigating the exact way that Beech Leaf Disease spreads, but this nematode is the prime suspect.

Beech Leaf Disease spreads to beech trees growing in a range of areas. There is no evidence that the steepness of the slope, sun orientation, or soil type affects the way this pathogen spreads.

As of now, there is no control over the spread of Beech Leaf Disease in eastern forests.

Which beech trees get Beech Leaf Disease?

Beech Leaf Disease affects familiar beech tree species throughout Connecticut, which are:

  • American beech (Fagus grandifolia)
  • European beech (Fagus sylvatica)
  • Oriental beech (Fagus orientalis)

In Connecticut, you’ll find our native beech in both cool, moist forests and in designed landscapes.

You’ll find European beech and its cultivars (copper beech, weeping beech) used as ornamental or landscape specimen trees.

Our state’s native forest beech trees are especially notable for their ecosystem contributions. Beech trees provide:

  • A regular food source for birds, bears, and other wildlife who rely on their nuts
  • Canopy nesting habitat for songbirds and small animals
  • Soil nutrient cycling from forest leaf litter
  • Shading cool forest understory plants to maintain species diversity.

The American beech is a key forest species in northeastern forests, and particularly in Connecticut, where it is one of the dominant tree species. The loss of our native beech trees would dramatically change the look of our forests.

Where did Beech Leaf Disease come from?

We can’t be sure where Beech Leaf Disease originated, but the nematode associated with it was first identified in Japan in 2004.

Scientists in the USA first documented the destructive nematode responsible for spreading this disease in Ohio, in 2012.

Since then, Beech Leaf Disease has spread to other eastern states (including Pennsylvania, New York, Rhode Island, and Massachusetts) and north into Canada.

Is Beech Leaf Disease in Connecticut?

Yes. Scientists from Connecticut’s Agricultural Experiment Station first verified Beech Leaf Disease near Stamford, Connecticut in 2019.

Currently, the disease is widespread in the state.

As of July 2021, counties in Connecticut that have recorded Beech Leaf Disease include:

  • Fairfield
  • Litchfield
  • Middlesex
  • New Haven
  • New London
  • Tolland
  • Windham
Beech tree saplings infected with beech leaf disease.

Beech leaf disease can kill saplings within 2 to 5 years

What does Beech Leaf Disease do to beech trees?

Beech Leaf Disease kills beech trees. With no known cure, the disease is spreading quickly through our forests. Scientists estimate that it will kill millions of native beech trees.

As the name suggests, Beech Leaf Disease affects the tree’s leaves. Infected leaves become unable to photosynthesize (this is the process every tree relies on to create food energy to grow and to store for dormant-season use).

The loss of food energy leads to a loss of vigor and general tree health. Once a beech tree loses its vigor, it is a magnet for other destructive organisms such as fungi and insects. We’ve also seen more anthracnose on affected trees although that’s not necessarily related to Beech Leaf Disease infection.

After becoming infected with Beech Leaf Disease, a beech sapling can die within two to five years. Mature beech trees may take a few more years to succumb but will die too.

Dark bands on beech leaves infected with beech leaf disease

What are the symptoms of Beech Leaf Disease?

It’s the leaves and buds of a beech tree that show the symptoms of Beech Leaf Disease.

As soon as an infected beech tree opens its leaf buds in spring, the disease will be visible in its new leaves. This is because the microscopic nematodes feed on leaf buds.

To see whether a tree is showing symptoms of Beech Leaf Disease, stand underneath a beech tree’s spreading crown and look up at the underside of the leaves. Look for striped bands of darker green leaf tissue between the leaves’ large veins.

These banded areas indicate leaf bud feeding and nematode egg-laying has happened. The dark green banding of interveinal leaf areas is unique to Beech Leaf Disease, making it an easy identification tool.

From the top of beech leaves, look for scattered sections of thickened, yellow leaf tissue. These yellow or dried leaf areas can fall out and make leaves look tattered or torn.

As Beech Leaf Disease spreads in a tree and symptoms worsen, you will see:

  • Leaves curling, cupping, and wrinkling
  • New leaf buds becoming stunted and dying
  • New leaf growth that’s yellowed and undersized
  • Increased leaf drop and a thinning tree canopy
  • Increased secondary diseases or infestations because the tree is stressed from disease

Ultimately, the whole beech tree will decline and die.

NOTE: Any symptoms of Beech Leaf Disease you see at spring bud break are the result of infection in the previous year.

Are symptoms visible throughout the entire tree?

Beech Leaf Disease often spreads from the base of a tree’s crown to its top, but there is no consistent pattern.

You may see healthy leaves interspersed with mildly or severely diseased leaves on the same twig or branch anywhere on a beech tree. It can be hard to spot Beech Leaf Disease in a large tree’s crown if there are only a few scattered areas of leaf damage showing.

Is there a treatment for Beech Leaf Disease?

Currently, there is no proven treatment for controlling Beech Leaf Disease.

Some tree care companies are treating beech trees with nemacides. Nemacides treat soil-dwelling nematodes but are being tested on infected beech trees for their effectiveness against Beech Leaf Disease.

It’s important to remember that any successful nemacide treatments would be effective only for residential trees; our forests can’t be treated with this method.

Until we find a treatment for Beech Leaf Disease, managing this deadly disease should focus on prevention.

How can we prevent Beech Leaf Disease?

Prevent the introduction of Beech Leaf Disease into uninfected areas of forests and landscapes by respecting quarantines and following rules. It really can take only one person moving one infected tree to spread this devastating disease to new areas.

Monitor beech trees regularly and consistently for disease symptoms. For landscape trees, keeping beech trees healthy with regular irrigation and fertilization is a good defense against many pests and diseases.

⇒ Report any incidents of confirmed Beech Leaf Disease to Connecticut’s Plant Disease Office.

Why is Beech Leaf Disease showing up now?

There are several scientific suggestions about why we’re seeing Beech Leaf Disease spreading so rapidly and putting Connecticut’s forests at risk. Explanations fall into three categories: weather events, human actions, and ecosystems.


  • Strong winds – Severe weather events can spread diseases, as many tiny organisms are wind-borne. Hurricane-level winds carry and then drop living organisms (such as tiny insects), and diseases in new locations.
  • Heat and drought – Beech trees are particularly sensitive to weather extremes and are less resilient than other broadleaf tree species. Stressed trees are more likely to develop diseases, and Beech Leaf Disease spreads easily from tree to tree.

⇒ Read more about how climate change affects forests.


  • Infected nursery tree stock – Distributing infected beech trees (even unknowingly) provides an ideal route for Beech Leaf Disease to spread across counties, states, and regions.
  • Logging or removing infected beech trees for lumber or firewood – Moving beech wood or green waste that carries Beech Leaf Disease automatically introduces the disease to new areas. Don’t move firewood!
  • Digging up forest saplings – Removing infected beech saplings and transplanting them in new locations spreads the Beech Leaf Disease to uninfected areas.

The undersides of beech leaves in a Connecticut forest showing black bands, a sign of beech leaf disease


  • Beech Leaf Disease may spread through entwined root systems in forest stands or clusters of beech trees.
  • Songbirds can carry and transfer the disease as they move through forests. Some overwintering birds, such as finches, regularly feed on beech buds in winter.
  • Insects, such as spider mites, have been found covered with nematodes and may carry them to other trees.
  • Rain and water splash from infected trees may transfer Beech Leaf Disease to nearby trees.


There are many diseases that affect Connecticut’s trees and homeowners can’t be expected to identify them all. That’s why getting a professional diagnosis is so important.

If you are worried about Beech Leaf Disease (or about any other tree problems), our Connecticut Licensed Arborists are here to help with consultations and tree health evaluations.

Your trees are invaluable assets and we want to help keep them vigorous and long-lived. Give us a call today; we’re always happy to answer questions and help you with your trees!

** All information and images of beech leaf disease symptoms courtesy of Dr. Robert E. Marra, Connecticut Agricultural Experiment Station.